A database is a collection of stored data that is logically related and that is accessible by one or more users or applications. A popular type of database is the relational database management system (RDBMS), which includes relational tables made up of rows and columns (also referred to as tuples and attributes). Each row represents an occurrence of an entity defined by a table, with an entity being a person, place, thing, or other object about which the table contains information.
Premium database products implement their own file systems to facilitate the storage of data in database objects, e.g., tables, indexes, etc. The motivation for doing this is that it enables the database vendor to optimize the file system for their database and targeted customer class of applications. However, a common trait of a database vendor developed file system is that the file system supports only a specific class of storage devices possessing a fixed set of characteristics, such as storage that is reliable, e.g., protected from single device failures and single storage path failures, storage that is non-volatile, storage that is re-writeable, or other storage device characteristics. Such file systems thus may be characterized as homogeneous with respect to the type of storage devices that it may support. This approach is suitable if the database customer's perceived value of their data matches the cost of the class of storage they are permitted to attach to their database system.
In recent times, however, there has been a growing desire to store what is referred to as “nearline” data in the database. Nearline data is data that the user desires to have online and available, but only wishes to access on an occasional or infrequent basis. Examples of nearline data include, for example, compliance data, fixed content, bulk storage, or short term data that is archival in nature. Since the data is only occasionally or rarely accessed, the desire is to place it on storage that is much more economical than storage used for frequently accessed data. Problematically, storage that tends to be less expensive also tends to be less reliable than more expensive storage. Also, if one considers accommodating “fixed content,” i.e., non-changing data, it is desirable to place the fixed content on a write-once storage rather than a re-writable storage. However, contemporary homogeneous file systems are not capable of accommodating storage devices having markedly different storage characteristics.